The invention relates generally to piping specialty items. More particularly, the invention relates to a sight flow indicator which allows optical monitoring of fluid in a piping system.
Sight flow indicators have long been known in the art. Prior art sight flow indicators commonly comprise a transparent body or an armored metal body with one or more glass viewing ports, a fluid inlet port, and a fluid outlet port. Sight flow indicators are commonly used in piping systems, such as petrochemical piping systems, to allow an operator to visually monitor the flow of fluids therein. However, sight flow indicators generally permit monitoring of bulk fluid flow only and do not provide a ready indication of the constituents of the bulk flow. For example, oil pumped from a well is likely to include produced water, produced gases, sediment, and other particulate matter. Although a conventional sight flow indicator allows an operator to monitor such bulk well flow, an operator generally cannot determine visually what percentage of the bulk well flow comprises, for example, oil vs. produced water.
Prior art techniques for determining the composition of oil versus produced water in bulk oil well flow generally involve collecting the bulk flow or a sample thereof in a separation vessel, or tank, and allowing the gases, the produced oil, the produced water, and the sediment to separate and stratify (a process that can take several days). Once the produced water and oil have been separated, the relative percentages of each can be readily determined. However, this technique operates on a sampling, not continuous, basis, and it does not provide real-time data that may be of vital importance to a well operator.
Techniques have been developed for analyzing multi-fluid flow to determine the percentages of the various components present therein. One such technique involves optical analysis of the flowing fluid. The technique may be implemented by associating an optical analyzer, such as a spectrometer, with the viewing region of a conventional sight flow indicator so that the optical analyzer can monitor and analyze the fluid flowing through the pipeline. Although this technique offers analysis and data output on a real-time or near real-time basis, its accuracy suffers when the fluid contains entrained gas and particulate matter. Accordingly, it would be desirable to provide a sight flow indicator which can provide a substantially gas- and particulate-free sample to a viewing region of the sight flow indicator.
It is an object of the invention to provide a sight flow indicator for use in piping systems which provides optical indication of fluid flow therethrough.
It is another object of the invention to provide such a sight flow indicator which is configured to disentrain gas and particulate matter from at least a portion of the flow indicator which comprises a viewing window.
It is a further object of the invention to provide such a sight flow indicator which can be used in conjunction with an optical analyzer which can determine the relative percentages of different types of liquids, such as oil and produced water, comprising the bulk fluid flow through the sight flow indicator.
The apparatus of the present invention is a sight flow indicator which has an inlet port and an outlet port, with an expansion chamber disposed therebetween. The expansion chamber includes a diverging region, a main body portion, and a converging region. The diverging region is located between the inlet port and the main body of the expansion chamber, and the converging region is located between the main body of the expansion chamber and the outlet port. The main body of the expansion chamber has a relatively large cross section, compared to the inlet and outlet ports. In a preferred embodiment, one or more flow baffles are located within or near the inlet port, proximate the diverging region.
A sampling cavity extends radially outward from the main body of the expansion chamber. In a preferred embodiment, the sampling cavity is comma-shaped and has a thin cross section, compared to the main body of the expansion chamber, to allow for optical analysis of relatively opaque liquids, such as heavy crude oil. The sampling cavity includes one or more transparent viewing windows.
In use, the sight flow indicator is installed as an in-line element in a piping system. Typically, the inlet and outlet ports are sized to substantially match the inlet and outlet piping.
In a preferred embodiment and installation, the sampling cavity lies in a substantially horizontal plane and fluid flows through the flow indicator in a substantially horizontal direction. Also, in a preferred embodiment, a portion of the expansion chamber lies above the sampling cavity and a portion of the expansion chamber lies below the sampling cavity.
As a fluid flows through the inlet port and across the baffles, the fluid""s velocity is increased and its pressure is reduced as a consequence of the reduced flow area proximate the baffles. This effect tends to disentrain gases from the fluid. As the fluid exits the inlet port and baffle region and flows into the expansion chamber, the fluid""s flow velocity is reduced as a consequence of the increasing cross sectional area of the diverging section of the expansion chamber. As a consequence of the initial increase and subsequent decrease in flow velocity, and of the expansion chamber""s overall configuration, gases entrained in the fluid tend to rise out of the fluid into an upper region of the expansion chamber, to a level above the sampling cavity. Similarly, solids and particulate matter entrained in the fluid tend to settle into a lower region of the expansion chamber, to a level below the sampling cavity.
As the fluid passes over the baffles, at least a portion of the fluid flow is diverted away from the bulk flow centerline. An eddy current is thus established within the expansion chamber and through the sampling cavity. A person or an optical device can view the flow through the viewing window in the sampling cavity.
Since the sampling cavity lies substantially between the upper and lower regions of the expansion chamber, and because entrained gases and solids have risen and settled into the upper and lower regions of the expansion chamber, respectively, the flow through the sampling cavity and past the viewing window is relatively free from entrained gas and particulate matter. Consequently, optical detection means can be readily employed to analyze and determine the makeup of the liquid flow past the viewing window.
As the fluid flows out of the expansion chamber and through the outlet port, the fluid flow reconverges. Gases and solids that were disentrained from the bulk flow stream in the expansion chamber are substantially flushed out of the expansion chamber and into the outlet piping. The fluid""s flow velocity and flow pressure are returned toward their upstream levels, subject to pressure losses caused by the sight flow indicator apparatus. But for such pressure loss, the flow through the remainder of the piping system is substantially unaffected by the sight flow indicator.